Look for frost on the service panel in the rear of the freezer. If you see any then you most likely have a defrost issue. The fan is working harder than normal maybe rubbing against ice if that is the case. Only way to know for sure is look. Their are some tests you can do from the control board. Shawn Ryan has a nice video:

About the icons: The beer is tip link, if a tech saves ya some money buy em a 6 pack. The small green square=personal message. The green dot is a link to my web page on appliance repair and other general BS I love to post. The letter sends me email.I love fan letters! LOL